Moneyball: how a third of the Yankees' budget bought a 20-game streak.

Math and sports have an intricate connection. So why not write something about sports? This leads to our story #32, which takes off from the book (later a movie starring Brad Pitt) Moneyball.

The Oakland Athletics baseball team had a limited budget for salaries compared to other franchises, and so needed to find players who were either undervalued or showing potential but unnoticed by rivals with deeper pockets. They did it using math — sabermetrics.

The statistics commonly used at the time were batting averages, runs batted in and stolen bases. Taking a more radical approach, the Athletics developed a rigorous process of statistical analysis, digging into the stats that gave a more solid foundation for assessing a player's performance:

• On-base percentage — how often a batter reaches base for any reason other than a fielding error, which turned out to be a meaningful way of measuring a batter's strike rate.
• Slugging percentage — total bases divided by at-bats, which determines the power of a hitter more accurately than a statistic like the number of home runs.

Rigorous analysis had shown that on-base and slugging percentages are better indicators of offensive success, and the team became convinced that these qualities were cheaper to obtain on the open market than historically valued ones like speed and contact. These observations often flew in the face of conventional baseball wisdom and the beliefs of many scouts and executives.

Using such figures to recruit potential stars at a fraction of their market value, the Athletics emerged as the powerhouse of the American League West. In 2002 they set an American League record winning streak of 20 games in a row — not bad for a franchise operating with around a third of the financial clout of the New York Yankees.

The team calculated, analysed and economised its way from a regional division challenger to a play-off powerhouse between 1996 and 2004 — a period now referred to as "the Moneyball years".